We have to distinguish between Technical "Halt" and Commercial "Stop". A technical halt is a necessity due to change of loco-pilots, water change, pantry replenishment, guard change - staff changes necessary while crossing a zone - etc.
Itarsi is a technical halt for TN Exp and not a commercial stop. The decision on a commercial stop is taken based on effect on running time, demand at local station, commercial viability. TN Exp probably does not have a commercial stop at Itarsi due to the effect it will have on its overall running...
more... time.
PRESTIGE status has nothing to do with halts and stops.